These DAV Class 6 Science Notes and DAV Class 6 Science Chapter 5 Notes – Changes Around Us act as excellent revision resources, particularly in preparation for board exams.
Changes Around Us Class 6 DAV Notes
→ Fast Change: The time required for some changes is very less. Such changes are called fast changes. Example: change of milk into cheese.
→ Slow Change: The time required for some changes is too much. Such changes are called slow changes. Example: milk changing into curd, rusting of iron, etc.
→ Reversible Change: Some changes can be reversed by removing the cause of the change. Such changes are called reversible changes. Example: Melting of ice, inflation of balloon, etc.
→ Irreversible Change: Some changes cannot be reversed. Such changes are called irreversible changes. Example: burning of paper, germination of seed, etc.
→ Physical Change: A change in which no new substance is formed is called physical change. Most of the physical changes are reversible. Example: melting of ice, breaking of glass tumbler, cutting a piece of paper, etc.
→ Chemical Change: A change in which a new substance is formed is called chemical change. Most of the chemical changes are irreversible. Some chemical changes can be reversed by using chemical means. Example: burning of paper, cooking of food, growth in a child, burning of wood, change of milk into curd, etc.
→ Changes involve energy: A change always involves energy. Energy’ is either absorbed or released during a change. For example, when candle is burnt, energy is released. Similarly, when ice melts, it happens because the ice absorbs energy.
→ Reversible change: A change which can be reversed by removing the cause of change.
→ Irreversible change: A change which cannot be reversed.
→ Desirable change: A change which is desirable and beneficial.
→ Undesirable change: A change which is not desirable and harmful.
→ Chemical reaction: Chemical change is also known as chemical reaction.
→ Rusting of iron: Formation of a brownish layer on iron, because of the reaction of iron with atmospheric moisture and air is called rusting.
→ Burning: A chemical change during which energy is released along with light.
→ Melting: A physical change during which a material changes from solid to liquid.
→ Freezing: A physical change during which a material changes from liquid to solid.
→ Solidification: Freezing is also known as solidification.
→ Evaporation: A physical change during which a material changes from liquid to gas.
→ Condensation: A physical change during which a material changes from gas to liquid.
→ Liquefaction: Condensation is also known as liquefaction.